Residential magnetic fields exposure and childhood leukemia: a population-based case-control study in California

Abstract

Residential magnetic fields exposure and childhood leukemia: a population-based case-control study in California Kheifets L, Crespi CM, Hooper C, Cockburn M, Amoon AT, Vergara XP. Residential magnetic fields exposure and childhood leukemia: a population-based case-control study in California. Cancer Causes Control. 2017 Sep 12. doi: 10.1007/s10552-017-0951-6. Abstract PURPOSE: Studies have reported an increased risk of childhood leukemia associated with exposure to magnetic fields. We conducted a large records-based case-control study of childhood leukemia risk and exposure to magnetic fields from power lines in California. METHODS: The study included 5,788 childhood leukemia cases (born in and diagnosed in California 1986-2008) matched to population-based controls on age and sex. We calculated magnetic fields at birth addresses using geographic information systems, aerial imagery, historical information on load and phasing, and site visits. RESULTS: Based on unconditional logistic regression controlling for age, sex, race/ethnicity, and socioeconomic status using subjects geocoded to a basic standard of accuracy, we report a slight risk deficit in two intermediate exposure groups and a small excess risk in the highest exposure group (odds ratio of 1.50 (95% confidence interval [0.70, 3.23])). Subgroup and sensitivity analyses as well as matched analyses gave similar results. All estimates had wide confidence intervals. CONCLUSION: Our large, statewide, record-based case-control study of childhood leukemia in California does not in itself provide clear evidence of risk associated with greater exposure to magnetic fields from power lines, but could be viewed as consistent with previous findings of increased risk. ncbi.nlm.nih.gov Excerpts Over 35 epidemiologic studies have investigated the association of childhood leukemia with residential low- frequency magnetic fields or physical surrogates of magnetic fields [1]. Three pooled analyses have found an increased risk of childhood leukemia for relatively high estimated residential magnetic field exposure [2, 3, 4]. The consistent association found between childhood leukemia and average magnetic field exposure above 0.3- 0.4 µT could be due to chance, selection bias, misclassification, other factors which confound the association, or true causal relationship. As explanation for both individual results and pooled efforts is lacking, selection bias seems as the most likely explanation, but uncertainty remains and other explanations outlined above are possible. This study aims to address this uncertainty by minimizing bias, misclassification, and chance. The California Power Line Study is funded by the Electric Power Research Institute. The authors declare no conflicts of interest. [The estimates of leukemia risk for 0.4 or greater microTesla exposure ranged from 1.48 - 1.55 (all p-values > .25). There were only 17 cases and 11 controls in this subgroup so the study has limited statistical power.]

AI evidence extraction

Main findings

In unconditional logistic regression adjusted for age, sex, race/ethnicity, and socioeconomic status, the study found a slight risk deficit in two intermediate magnetic-field exposure groups and a small excess risk in the highest exposure group (OR 1.50, 95% CI 0.70–3.23). Subgroup/sensitivity and matched analyses were similar, and estimates had wide confidence intervals.

Outcomes measured

• childhood leukemia

Limitations

• Wide confidence intervals
• Limited statistical power in the highest exposure subgroup (e.g., 17 cases and 11 controls for ≥0.4 µT mentioned in excerpts)
• Exposure estimated from birth addresses using GIS/aerial imagery/historical load and phasing/site visits (potential exposure misclassification not fully characterized in abstract)

Suggested hubs

• occupational-exposure (0)

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    "study_type": "case_control",
    "exposure": {
        "band": "ELF",
        "source": "power lines (residential)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Children born in and diagnosed in California (1986–2008)",
    "sample_size": 5788,
    "outcomes": [
        "childhood leukemia"
    ],
    "main_findings": "In unconditional logistic regression adjusted for age, sex, race/ethnicity, and socioeconomic status, the study found a slight risk deficit in two intermediate magnetic-field exposure groups and a small excess risk in the highest exposure group (OR 1.50, 95% CI 0.70–3.23). Subgroup/sensitivity and matched analyses were similar, and estimates had wide confidence intervals.",
    "effect_direction": "unclear",
    "limitations": [
        "Wide confidence intervals",
        "Limited statistical power in the highest exposure subgroup (e.g., 17 cases and 11 controls for ≥0.4 µT mentioned in excerpts)",
        "Exposure estimated from birth addresses using GIS/aerial imagery/historical load and phasing/site visits (potential exposure misclassification not fully characterized in abstract)"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "childhood leukemia",
        "residential exposure",
        "magnetic fields",
        "power lines",
        "ELF",
        "case-control",
        "California"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0,
            "reason": null
        }
    ]
}

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